It is the purpose of the present investigation to ascertain and describe the way in which the concept of heart failure (cardiac insufficiency) arose and developed. Information made available through recent research confirms the earlier surmise that the course of development was very complex. Therefore the investigation will be limited to the period beginning with Carolus Piso (1618) and will end with the work of Morgagni (1761). Medical writings published during that span will be studied; those illustrating aspects of the development will be translated, wholly or in part, with introductions and annotations. The evidence collected will make it possible to establish the course of development.